The I-535 High Bridge opened to traffic on December 2, 1961, replacing the Interstate Bridge. At just shy of 8,000 feet, this was the longest bridge in Minnesota when it opened. If you include the overland approaches, the overall bridge length is 10,775 feet. The bridge has since been renamed after John A. Blatnik, a champion of the High Bridge project.

A need for a new Duluth harbor crossing was seen as early as 1930. Local officials lobbied for a new bridge. Another concept that was put forward was a plan for a tunnel under the harbor, much like the I-10 George Wallace Tunnel in Mobile, Alabama. Between the depression and World War II, these proposals remained unfunded. The bridge issue surfaced again in the mid-1950s. This time, money was available though the Interstate Highway program. The route was designated I-535. Construction began in the late 1950s, with a grand opening in late 1961. The Interstate Bridge, located below and slightly east of the High Bridge, closed within a year of the opening of the new I-535 High Bridge.

The bridge was officially named after John A. Blatnik on September 24, 1971. Blatnik was born on the Iron Range. He served as state Senator from 1940 to 1944 and also served in the US Army Air Force. After WWII, Blatnik served in the US House of Representatives from 1947 to 1975. Blatnik also was a champion of the Saint Lawrence Seaway project.

Major reconstruction of the Blatnik bridge occurred in 1992 and 1993. The bulk of the work was to widen the bridges to add room to the shoulders, and to install a center divider. There was also a three year project to paint the bridge from end to end.

While Minnesota has one entry in the National Bridge Inventory for the Blatnik Bridge, Wisconsin maintains 5 entries as follows:

    NBI #B16000500050000, 2,241 Feet, Girder Span, Crosses WI-35.
    NBI #B16000500020000, 697 Feet, Girder Span, Crosses Howards Pocket.
    NBI #B16000500030000, 1,884 Feet, Girder Span, Crosses Soo Line Railroad.
    NBI #B16000500010000, 1,140 Feet, Arch Span, Crosses Saint Louis Bay.
    NBI #B16000500040000, 2,022 Feet, Girder Span, Crosses Garfield Ave.

If you add up these spans, you get 10,225 feet. This is 2,245 feet longer than what Minnesota reports in their NBI entry. Minnesota apparently does not count the bridge sections that cross WI-35 on the Superior end of the bridge. It is also possible that Minnesota recognizes a different northern endpoint for the bridge. As evidence, a photo below shows that there is landfill between the Blatnik Bridge and the Garfield Avenue Bridge. If Wisconsin considers the Garfield Avenue interchange to be part of the Blatnik Bridge, that could account for the 2,245 foot discrepancy.

In early 2008, the Minnesota state Department of Transportation started a program to inspect and audit all truss bridges in Minnesota. On May 6, 2008, MN-DOT announced that they discovered that structural load calculations had not been run on the Blatnik bridge when it was modified in the early 1990s. They were concerned that the bridge might be unsafe given that a similar situation lead to the collapse of the I-35W bridge in Minneapolis. Once these calculations were completed, it was discovered that 16 critical gusset plates did not have a sufficient safety margin when the extra weight of the additional two inch depth of concrete was added to the bridge deck. As a result, two lanes of the bridge were closed, and remained closed until the bridge could be repaired. It turns out that the fix was relatively straight forward. The biggest trick would be rigging the access and bringing in equipment to locations so high over the water. In all, 16 gusset plates were strengthened by adding angle iron strengtheners or plate doublers. The project was completed later that summer.

The photo above is the east face of the main truss span of the Blatnik Bridge as seen from the north end of Connor's Point in Superior, Wisconsin. The tip of Connor's Point is posted for No Trespassing, so it wasn't possible to get to the northern tip of the island. If you look closely between the vehicles and the yellow post, you can see a line of pilings leading into the water just under one of the trees. Those are the remains of the southern end of the Interstate Bridge, which once carried trains and traffic across a swing bridge between Duluth and Superior.

These two photos are views of the Blatnik Bridge taken from an overpass on US-53 high up on Miller Hill. The photo above is a close-up view of the main truss span, while the photo below is an overview of the entire bridge.

These two photos are views from the Thompson Hill rest area on I-35, 5-1/4 miles west of the bridge site. These are late evening photos taken in low light just as the sun was setting behind the bluffs. While shadows were already creeping across the city, the bridge structure was still lit up with the last rays of sunlight before darkness.

The photo above is looking north towards Duluth from the Harvest States grain elevator. It is amazing that there are relatively few locations to get a good unobstructed view of such a large structure. The photo below shows the Blatnik Bridge looking southbound from the Garfield Avenue exit ramp.

Two views of the main span from slightly different angles. These photos were taken from the DNR boat launch parking lot that sits directly under the north end of the structure. Notice that the truss section not only includes the main arch, but that the truss also extends back one span on each side of the main span. This is in contrast to the more modern Bong Bridge just upstream where the arch structure only covers the main span. Also notice the horizontal lines in the concrete on the piers. It appears that the piers may be made out of segments that were precast and installed in this location as part of assembly. Using such a strategy would have vastly shortened the time required to build the bridge.

Here are two photos taken from a distance, each showing a large portion of the bridge. The above photo was taken from the Bong Bridge by pointing a camera out of the passenger window of my truck. One can see a large ship passing under the main span. The large Harvest States elevator complex is on the right side of the photo. The photo below was shot from Thompson's Hill near the I-35 Rest Stop.

The remaining photos are of a typical crossing from Superior to Duluth. The photo above is the big green sign at the start of the bridge, indicating the start of Interstate 535. The grain elevator complex is the Harvest States Cooperative facility. Below is the initial upward climb from ground level to about the 90 foot level. It feels very much like the initial climb on a roller coaster. The speed limit is 55 MPH, which was raised from 45 MPH after the major rebuild in the early 1990s.

The photo above is reaching the top of initial climb. The photo below is the causeway turn over Howards Bay. Duluth can be seen in the background, and Minnesota Point is off to the right.

These two photos show the trip across Howard's Bay towards the final climb to the 125-foot level for them main span. The Cargill grain elevators are visible to the right of the highway. In addition, the General Mills elevator is visible in the distance on the photo below (below the yellow highway sign).

In these two photos, we cross into the main arch section, then pass through the arch. The suspension cables that holds up the roadway are clearly visible on the right side of the photos. The cables are installed in groups of four.

After passing though the arch, we start downhill into Duluth. This gives us a better view of the Duluth side of the harbor. The photo below shows the Garfield Avenue interchange. This is the only exit on I-535, and it provides access to the Duluth harbor waterfront and to the park under the Blatnik Bridge. That park includes the surviving section of the old Interstate Bridge.

Back on flat land, we are rapidly facing the choice of heading north on I-35 towards downtown Duluth, south on I-35, or staying on US-53 to go up Miller Hill towards the mall and airport area on top of the bluffs. The rail yard to the right is one of the many BNSF rail yards in the Twin Ports area. The photo below shows the Minnesota state line sign. While most states use steel signs for the state line, both Minnesota and Wisconsin put up monuments at the state line.

In the photo above, we take the I-35 north option towards downtown Duluth. Enger Tower can be seen on the top of the bluff. Enger Tower was built during the depression as a tourist attraction. The base of the tower sits 531 feet above the Lake Superior water level.

The photo below is merging onto I-35 heading northbound. I-35 was put though in the early and mid-1980s. The section at the far end of the photo running to Lake Street opened in 1986. The final sections past downtown opened in the early 1990s. The section in this photo is built on an old railroad switching yard. The state funded part of the building of the Pokegama Rail Yard in Superior in order to get the lakefront land to build I-35.

These two photos are looking east towards the Blatnik Bridge on an early but cold autumn morning. The vantage point is looking between homes on the west side of Minnesota Point. The photo above is the main bridge truss span at the entrance to the inner harbor. The remaining span of the Interstate Bridge is visible on the right side of the navigation channel, while the Bong Bridge is visible in the distance. The photo below is the steel girder spans that cross the Howards Bay channel. The Harvest States elevator complex is located just behind the bridge, while the taller General Mills elevator complex is located a half mile to the west of the bridge.

These two photos are views from a boat dock located just to the east of the public boat landing parking area on Rice's Point. The photo above is looking south along the west face of the Blatnik Bridge, while the photo above is looking north along the west side of the approach spans.

The photo below is the northernmost of the four main span bridge piers. The segmented construction of the piers is easily visible in this view. The photo below is looking straight up at the underside of a steel girder bridge span. The steel girder spans were freshly sand blasted and painted in this view from the summer of 2010.

The photo above is looking up at the top of the northernmost main bridge pier. Note the 1960 date formed in the concrete. The photo below is the underside of the northern span of the large steel truss section of the bridge.

These two photos, and the five that follow, are views looking west from the remaining truss span of the Interstate Bridge. The photo above is the main navigation channel crossing, while the photo below are the steel girder spans leading to and crossing Howards Bay. Both photos are looking into the bright midday sun.

The photo above is looking west into the midday sun towards the main span of the Blatnik Bridge. The photo below is a close view of the northern transition from the truss span to the arch truss span. Note the gap in the steel between the two section of the bridge. The entire main arch hangs from two pin connections at each end of the bridge, with the truss spans at each end of the bridge acting as a cantilever. Note that some of the gusset plates are freshly painted. Those plates had extra steel plate doublers attached in the repairs in 2008.

The photo above is the northern of the three truss spans that comprise the main navigation channel crossing. The photo below is the approach spans at the north end of the bridge. The orange steel in the foreground are remains of the old Interstate Bridge.

The photo above is the main bridge pier on the north side of the navigation channel. Note the large steel dolphins that protect this bridge pier. The need for these dolphins were pointed out after a ship struck and collapsed the Sunshine Skyway Bridge in Tampa in 1980. The photo below is a marker located under the north end of the bridge near the parking area for the public boat landing.

The photo above is looking south along the east face of the Blatnik Bridge from the public boat landing at the southern tip of Rice's Point. The photo below is looking along the west face of the approach spans, also from the parking area of the public boat landing.

The photo above is the northern bridge abutment. The roadway running under the bridge is northbound Garfield Avenue, which splits and runs on both sides of the bridge abutment. The photo below is the third bridge span from the north abutment. The piers are aligned at an angle in order to run parallel to the railroad track that once passed under the Blatnik Bridge at this location. That railroad track was the approach to the Saint Louis Bay Bridge, a railroad crossing that featured two swing spans.

The photo above is looking south along the west face of the Blatnik Bridge from the locate of the photo above where the approach track to the old Saint Louis Bay Bridge once passed under the Blatnik Bridge. The photo below is where another railroad track passes under the Blatnik Bridge, located just north of the UPS facility on Rice's Point. This track once fed a small rail yard on the west side of the point.

These photos are two more views of the west face of the Blatnik Bridge as seen from the southern tip of Rice's Point. The photo above was taken from the edge of Garfield Avenue, while the photo below is a view from the entrance to the boat landing parking lot. I was nearly able to get this photo without any cars or people in the frame. Unfortunately, some bridge photographer had to park his blue Chevrolet HHR in the way. That would have been me. While I wish I had parked my car somewhere else, and I was apparently too lazy to go move it, it does serve as a good comparison to show just how massive this structure is.